At least Analog Devices and also Fairchild propose analog switches as level translators to interface eg 1.8V logic to 3.3V logic. I fail to recognize how this is going to work. The Low state is understood, it is just pulled down, but how is a 1.8V output high propagated to a 3.3V high by just a resistor ?
Apart from the analog switches, what alternative are there to interface an 1.8V FPGA to normal 3.3V or 5V logic ? Yes, switchable bidirectional, or auto bidirectional is preferred. Else what unidirectional solutions are there ?